Filling material for heat exchangers



Jan. 14, 1964 5. J. FRAENKEL FILLING MATERIAL FOR HEAT EXCHANGERS Filed March 16 1961 g I I IN VEN TOR. fzpizerzJ wag/M y 5W United States Patent 3,117,625 FILLING MATERIAL FOR HEAT EXCHANGERS Stephen J. Fraenlrel, Wilmette, lll., assignor to Stanray Corporation, Chicago, 111., a corporation of Delaware Filed Mar. 16, 1961, Ser. No. 96,098 4 Claims. (Cl. 165-185) This invention relates to a form of material specifically for use as a filling and packing of enclosed spaces employed for effecting the washing, drying, humidifying, heating, cooling, absorbing or mixing of a gas or gases, or for the eflicient transmission of heat through passages which are restricted and difficult of access.

The invention contemplates the use of small hollow globule-like bodies of spherical, elliptical or other shape, each being preferably reasonably smooth in all its external surfaces so that they will run or flow readily through a more or less restricted opening into a cavity and lodge about an irregularly shaped object of complicated cross section therein, filling in itself perhaps, for example, about 50% of the cross sectional area of the cavity. The material, being of the shape it is, will flow by gravity in and about the object within the cavity until the space not occupied by the object is filled with the material.

Referring now to the accompanying drawing forming part of this application and wherein like reference characters indicate like parts.

FIGURE 1 is a view partly in elevation and partly in section of a cask for transporting spent fuel elements to a reprocessing plant and showing the filling and packing material when poured into the cask.

FIGURE 2 is a cross section on the line 2-2 of FIGURE 1.

FIGURE 3 is a vertical section of the lower part of the cask of FIG. 1 but illustrating the filling material after having ruptured or exploded.

FIGURE 4 is a cross sectional view of one of the individual filling material units, and

FIGURE 5 is a view of one of the units after it has ruptured or exploded.

In the drawings 1 indicates a cask for the transportation of spent fuel elements from an atomic reactor to a reprocessing plant. Such casks usually comprise inner 2 and outer 3 spaced cylindrical containers with a lead shielding material 4 therebetween to prevent damaging rays to pass therethrough to the surrounding atmosphere. Within the inner container 2 are carried the spent fuel elements 5. When such elements are placed therein, they are usually quite radioactive and still quite hot and it is the object of this invention to provide a means for more quickly conducting the heat from said elements through the containers and shielding material to the atmosphere.

To this end the quite small hollow metallic bodies, illustrated at 8, are poured into the inner container 2 until the space about the fuel elements is filled with all of such bodies the space can hold.

These hollow bodies 8 are typically about /8 in longest diameter and are made of a material which is a good conductor of heat, such as copper or aluminum or other material, and which is relatively soft and ductile. The wall thickness of the hollow bodies is thin enough so that when subjected to temperatures of about 800 F. to 1000 F. in the cavity the expanding air within the hollow bodies will provide sufiicient internal pressure to cause the walls to burst or rupture, as suggested in FIG. 5, in such a manner that a mesh, made up of individual,

3,117,525 Patented Jan. 14, 1964 unconnected, components, is formed, thereby approximately doubling the surface area thereof for heat transfer or other means. The hollow bodies 8 are sufiiciently soft and ductile so that when they burst or rupture, the body material will not shatter into dust or the like, but will remain intact. This resulting structure could not have been inserted into the cavity in the first place because its geometry would not have permitted it to travel or flow through restricted passages.

After these bodies are inserted into the cavity and they settle about the object and they rupture, the surface-tovolume ratio thereof is greatly increased which facilitates heat transmission through radiation.

Also the increased surface would permit increased contact area between the elements of the structure which would improve the straight conduction of heat.

In the application of the material, shown in the drawings, of providing a heat transfer medium for packing about a spent fuel element from an atomic reactor in a cask for transportation to a reprocessing plant, the heat given off by the fuel element would cause the medium to pop or rupture, greatly increasing the thermal conductivity.

In other applications, where no natural heat is generated, hot gases would be passed through the filled space to cause the medium to rupture or burst, after which the filling material in the space could fulfill any desired processing function at any temperature.

Thus it is seen that the medium provides a most convenient means of completely filling restricted areas, and, being convertible to a different shape, of doubling its surface area for heat transfer or any other desired function.

It is another concept of the invention, where lower temperatures only are available, to form the hollow bodies with external score lines so that they would be caused to burst or rupture when subjected to lower temperatures, or, in other words, would rupture with less internal pressure because of the weakened body wall, and result in a coarser mesh.

I claim:

1. The combination with a hollow cask having a spent fuel element therein, of a heat transfer medium comprising small convertible hollow globule-like geometrical structures enclosing therein gaseous atmosphere, said structures being reasonably smooth in all external surfaces, the structure walls being of relatively soft and ductile metallic material so that when subjected to a predeter mined degree of heat will cause internal expanding pressure of said gaseous atmosphere sufiicient to cause said structure walls to rupture and be converted thereby into an interwoven mesh, thereby greatly increasing the surface-to-volume ratio thereof and facilitating heat transmission.

2. The combination with a cask having a chamber therein and a spent atomic fuel element in said chamber for transportation to a reprocessing plant, of a heat transfer medium for filling the space about said fuel element in said chamber, said medium comprising convertible hollow metallic geometrical structures, gaseous atmosphere therein, said structures being reasonably smooth in all external surfaces to facilitate flowing by gravity to fill the space about said atomic fuel element, said structure wall being of a thickness in relation to the heat to which it is subjected in said cask to cause internal expanding pressure of said gaseous atmosphere sufficient to rupture said walls, thereby converting said structures into an inter- 3 4 Woven mesh, greatly increasing the surface-to-volume are provided with external score lines to weaken said walls ratio thereof and facilitating heat transmission from said whereby they rupture with less internal pressure and result cask through said chamber wall to the surrounding atmosin a coarser mesh. phere.

3. The structure of claim 1, said interwoven mesh pro- 5 References C1195 in the file 0f thls pilltelflt vided by said ruptured bodies being made up of individual, UNITED STATES PATENTS unconnected, components whereby the surface area thereof a n is at least approximately doubled for heat transfer or 2, 22 211111}? Aug. 47, 1940 other means. 2, 01,421 Thanlng June 24-, 1952 4. The structure of claim 1, wherein the structure Walls 10 24,556 isfl r Jan. 6, 1953 

1. THE COMBINATION WITH A HOLLOW CASK HAVING A SPENT FUEL ELEMENT THEREIN, OF A HEAT TRANSFER MEDIUM COMPRISING SMALL CONVERTIBLE HOLLOW GLOBULE-LIKE GEOMETRICAL STRUCTURES ENCLOSING THEREIN GASEOUS ATMOSPHERE, SAID STRUCTURES BEING REASONABLY SMOOTH IN ALL EXTERNAL SURFACES, THE STRUCTURE WALLS BEING OF RELATIVELY SOFT AND DUCTILE METALLIC MATERIAL SO THAT WHEN SUBJECTED TO A PREDETERMINED DEGREE OF HEAT WILL CAUSE INTERNAL EXPANDING PRESSURE OF SAID GASEOUS ATMOSPHERE SUFFICIENT TO CAUSE SAID STRUCTURE WALLS TO RUPTURE AND BE CONVERTED THEREBY INTO AN INTERWOVEN MESH, THEREBY GREATLY INCREASING THE SURFACE-TO-VOLUME RATIO THEREOF AND FACILIATING HEAT TRANSMISSION. 